In the field of refrigeration systems, for example, centrifugal pumps are typically used. These centrifugal pumps require continuous flow of liquid refrigerant through the pump via a bypass flow line to maintain stable operation of the centrifugal pump regardless of the refrigerant load requirements of the refrigeration plant. Even though the refrigerant load requirements of the refrigeration plant can vary from 0% to 100%, a minimum flow-through rate of the refrigerant continuously occurs through the centrifugal pump. The minimum flow-through is typically set for the pump by using either a fixed orifice, a manually adjustable valve disposed in the bypass flow line or appropriate sizing of the inner diameter of the bypass flow line.
As shown in FIGS. 1A-1C, a conventional refrigeration system 2 in a simplified form includes a refrigeration plant 4, a primary flow line 6, a pump 8 and a bypass flow line 10. The refrigeration plant 4 and the pump 8 are in fluid communication with one another via the primary flow line 6. A refrigerant 12, the flow of which being represented by arrows, flows clockwise, by way of example only, from the refrigeration plant 4 to the pump 8 via an upstream primary flow line section 6a and is pumped from the pump 8 to the refrigeration plant 4 via a downstream primary flow line section 6b. A primary flow line valve 14 is interposed in the downstream primary flow line section 6b and is positioned downstream of the bypass flow line 10. The bypass flow line 10 is in fluid communication with the primary flow line 6 with one end connected to the downstream primary flow line section 6b and an opposite end connected to the upstream primary flow line section 6a. The bypass flow line 10 enables circulation of at least a portion of the refrigerant 12 from a discharge (downstream) side of the pump 8 to a suction (upstream) side of the pump 8.
As illustrated in FIG. 1A, the primary flow line valve 14 is in a closed state and, as a result, there is no flow of the refrigerant 12 to the refrigeration plant 4 because there is no refrigerant required by the refrigeration plant 4. However, the pump 8 continues to operate in an idle mode in order to circulate the refrigerant 12 through the pump 8 to maintain its required minimum flow-through rate.
Thus, for the refrigeration system in FIG. 1A, the total flow TFR of the refrigerant 12 of the refrigeration system 2 is calculated as the sum of the minimum flow-through MFR of the pump 8 plus the flow rate requirements FRR of the refrigeration plant 4 stated as follows:TFR=MFR+FRR  (1).
By way of example only, assume that the minimum flow-through MFR of the pump 8 is 15 gallons per minute. Therefore, the total flow TFR, when the refrigerant load requirements of the refrigeration plant 4 is zero, is equal to 15 gallons per minute which is calculated as follows:TFR=15+0  (2).
As illustrated in FIG. 1B, the primary flow line valve 14 is in an opened state. More specifically, the primary flow line valve 14 is in a partially opened condition because the refrigerant flow requirements of the refrigeration plant is less than 100%, say, for example, 60% or 60 gallons per minute. In this case, the total flow rate TFR of the refrigerant 12 of the refrigeration system 2 is 75 gallons per minute which is calculated as follows:TFR=15+60  (3).
As illustrated in FIG. 1C, the primary flow line valve 14 is also in the opened state. More specifically, the primary flow line valve 14 is in a wide opened condition, i.e. fully opened condition, because the refrigerant flow requirements of the refrigeration plant is now 100% or 100 gallons per minute. In this case, the total flow TFR of the refrigerant 12 of the refrigeration system 2 is 115 gallons per minute which is calculated as follows:TFR=15+100  (4).
The refrigeration system 2 of FIGS. 1A-1C requires that the pump 8 has a pumping capacity of at least 115 gallons of refrigerant 12 per minute. Furthermore, the inner diameter of the primary flow line 6 at the suction side of the pump 8 and at the discharge side of the pump 8, particularly between the bypass flow line 10, must be sufficiently large to safely and effectively pass 115 gallons of refrigerant 12 per minute therethrough. Also, pump manufacturers typically build pumps in incremental flow capacities such as 100 gallons per minute, 125 gallons per minute and so on. In this case, the refrigeration system 2 would require a pump having a flow capacity of 125 gallons per minute. In turn, the primary flow line 6 at the suction side and discharge side of the pump 8 of the refrigeration system 2 should be designed to handle the flow capacity of 125 gallons per minute even though the flow capacity of only 115 gallons per minute for the refrigeration system 2 is required.
It would be beneficial to provide a bypass control apparatus that would enable a manufacturer, for example only, of the above refrigeration system to use a pump with a flow capacity of 100 gallons per minute rather than one having a flow capacity 125 gallons per minute or even 115 gallons per minute (even if one was available) without sacrificing the refrigeration capacity of the refrigeration system. Having such a bypass control apparatus would reduce the cost of manufacturing the refrigeration system, particularly with regard to a smaller capacity pump and a smaller diameter primary flow line at the suction side and discharge side of the pipe. Such a smaller capacity pump would result in less energy required to operate the refrigeration system without sacrificing refrigeration capacity. The present invention provides these advantages and benefits.